1. Field of the Invention
This invention relates in general to farriery, and in particular to the treatment of the equine diseases of founder and laminitis.
2. Description of Prior Art
Founder or laminitis in equines is a disease where the hoof wall separates from the underlying skeletal structure, referred to either as the coffin bone or the third phalanx. This occurs due to inflammation and deterioration of the laminae which holds the hoof wall to the third phalanx. The weight of the equine causes the coffin bone to rotate downward and the hoof wall to deform forward. Typically the equine will shift the distribution of weight onto the heels, which causes the flexor tendons to pull the coffin bone more, increasing and perpetuating the damage. Previous treatment of this problem comprised nailing corrective shoes to the hoof and, later adding therapeutic pads between hoof and shoe. Traditional types of shoes such as bar shoes, heartbar shoes or reversed shoes have been used. Therapeutic shoes are relatively new.
A horseshoe with a base within which filler could be added for support was described by Stubbe (U.S. Pat. No. 4,237,981). Murphy (U.S. Pat. No. 4,513,825), McKibbin (U.S. Pat. No. 4,605,071), Landi, et. al. (U.S. Pat. No. 5,509,484), and Colonel, et. al. (U.S. Pat. No. 4,823,883). All these described nail-on horseshoes with pads to absorb shock and for use in the treatment of lameness. Foster (U.S. Pat. No. 5,711,377) and Ovnicek (U.S. Pat. No. 5,727,633) both describe therapeutic pads with elevated heels used with horseshoes. The problems with these therapies is that they all use deflective cushions which don't provide solid support, and they all use horseshoes which are fastened to and support the hoof wall allowing continued deformation.
Several therapeutic horseshoes were described. Ovnicek (U.S. Pat. No. 5,727,633) described a horseshoe for treatment of lameness, however it avoids contact with the coffin bone. Hendrick (U.S. Pat. No. 4,794,991) used a concave shaped plate attached to a horseshoe while Mercer II (U.S. Pat. No. 4,422,509) used a horseshoe with an adjustable pin located under the coffin bone to pressure the coffin bone back into a normal position. While their concept is somewhat feasible, they do nothing to correct the deformation of the hoof wall. Brooks (U.S. Pat. No. 5,546,735) describes a horse hoof sandal with a triangular pad for frog support. This at least does not inhibit normal growth of the hoof wall, but uses a deflective pad placed on the frog rather than the coffin bone.
The use of a non-deflective support material was described by Techen, et. al. (U.S. Pat. No. 4,899,824) who injected the material between the hoof and a screen with a horseshoe for hoof sole support. Again, the horseshoe, being nailed to the hoofwall, prevents normal hoof wall growth Knudsen (U.S. Pat. No. 5,199,498) used a thermalplastic, polycaprolactone polymer, for hoof repair and as a moldable hoof pad. Beadle (U.S. Pat. No. 5,706,898) describes using a thermoplastic material on the frog of the hoof for treatment of laminitis. However, as their process has the equine stand on the unhardened material, the material flattens out allowing the hoof wall to contact the ground surface. No support remains for the anterior tip of the coffin bone, which is in front of the frog and behind the anterior hoof wall.
A common veterinarian surgical procedure for founder is to debride or remove the distorted hoof wall up to the area where the laminae are still intact. This allows the hoof wall to grow out without pressure from the ground surface. This procedure has the same mechanical objective as the present invention. However the surgical method opens the affected member to infection while necessitating daily cleaning and bandaging.
These applications, while contributing to the treatment of laminitis, all fall short of the necessary combination of the treatment principles. The anterior portion of the coffin bone of the hoof must be supported by a non-deflective, rigid surface while the hoof wall remains unsupported so that it can grow out without the horse's weight causing further deformation. Also, the toe-heel angle of the hoof should be raised to alleviate the tension of the tendons attached to the coffin bone, which otherwise would maintain the downward rotation caused by founder.